Like many have suggested over heating is the most common cause of this issue. The video card over heating can do this as well. The cheapest solution to start off your trouble shooting.
Purchase two cans of computer duster/canned air. Turn the computer off but leave it plugged in to keep it grounded.

Youtube how to video on cleaning out your processor with the canned air. If you have an after market video card with a large housing with fans built in, it's a nice trap for dust to get caked in there. Clean that out real good too. Give it a good 10min to evaporate before you turn it back on.

There are other causes that can cause this issue, however this is the most common out of all of them and a logical first step.

Ok folks enough about the heat problem. On my end The game quits when I am in a match...ONLY ON THE NA EAST SERVER.....Never crashes or quits on the NA WEST. Enough of the novice advice of overheating and other BS. It is Wots server that is the problem never happened to me before 8.6.

I've monitored my temps, and while WOT does increase my GPU temps somewhat, they're nowhere near maximum operating temperature (-30°C under M.O.T.) My CPU's core temps do not rise enough playing WOT to even mention; I usually see CPU core temps in the mid 50°C range tops playing WOT. I've had a recurring issue of my nVidia display driver stopping, but this only occurs playing WOT.

Meisgoot312's suggestion of running in windowed mode did seem to make my game FAR MORE STABLE, in fact I've only crashed once in three days running in windowed mode.
Are you WG programmers reading this? I suggest you look into the "windowed vs full-screen mode" areas of your code for bugs & glitches.